We investigated the oscillation of a dense stellar system which harbours a massive object, presumably a supermassive black hole, in its center. The central mass moves in response to the oscillation of the stellar system. This phenomenon may explain the asymmetric structure observed in M31 (Lauer et al., 1993), or NGC4486B (Lauer et al., 1996). Moreover, the motion of the central massive black hole may well induce the accretion of gas onto the black hole itself and ignite the activity in galactic nuclei. We first investigated the stability of a fluid disk around a massive object by linear modal analysis. Next, we performed N-body simulations for spherically symmetric, rotating, particle systems with a central mass.